The ionic model - IB DP Chemistry- Study Notes - New Syllabus 2025
The ionic model – IB DP Chemistry- Study Notes
IITian Academy excellent Introduction to the Particulate Nature of Matter – Study Notes and effective strategies will help you prepare for your IB DP Chemistry 2025 exam.
- IB DP Chemistry 2025 SL- IB Style Practice Questions with Answer-Topic Wise-Paper 1
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- IB DP Chemistry 2025 HL- IB Style Practice Questions with Answer-Topic Wise-Paper 1
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S2.1.1 – Ions
Ions:
- Charged particle that forms when an atom gains or loses electrons
- Positively charged Ions are called Cations.
- These lose electrons
- Negatively charged Ions are called Anions.
- These gain electrons.
- Charge is equal to the amount of electrons gained or lost
Cations from Group 1 , 2, and 3:
1. Group 1
- 1. Have one valence electron, so they tend to lose one electron and form 1+ ions.
2. Group 2
- Have two valence electrons, so they tend to lose two electrons and form 2+ ions.
3. Group 13 or 3
- Have three valence electrons, so they tend to lose three electrons and form 3+ ions.
NOTICE THAT FOR IONS, THE CHARGE IS LISTED AFTER THE NUMBER (Ca2+, Al3+).
OXIDATION STATES ARE LISTED WITH THE CHARGE BEFORE THE NUMBER (+2, +3).
4. Group 4
- Tend to not lose or gain electrons due to the amount of energy involved so they do not normally form ionic bonds.
Anions from Group 5 , 6, and 7:
1. Group 15 or 5
- Have five valence electrons, so they tend to gain 3 electrons and form 3- ions.
2. Group 16 or 6
- Have six valence electrons, so they tend to gain 2 electrons and form 2- ions.
3. Group 17 or 7
- Have seven valence electrons, so they tend gain 1 electron to form 1- ions.
ELECTRONS ARE GAINED OR LOST TO HAVE 8 ELECTRONS IN THEIR OUTER SHELL.
4. The names of anions ends with “ide”
Predicting Ionic Charge based on Electron Configuration:
- Atoms lose or gain electron to attain noble gas configuration
- Sodium atom Na → $1s^{2}2s^{2}2p^{6}, 3s^{1} or [Ne]3s^{1}$
- Sodium ion $Na^{1+} → 1s^{2}2s^{2}2p^{6} or [Ne]$
- Chlorine atom $Cl → 1s^{2}2s^{2}2p^{6}3s^{2}3p^{5} or [Ne] 3s^{2}3p^{5}$
- Chloride ion $Cl^{1-} → 1s^{2}2s^{2}2p^{6}3s^{2}3p^{6} or [Ar]$
Transition Elements:
- Transition elements have electron configurations that allow them to lose different amounts of electrons from their d-sublevels.
- They can form more than one stable ion.
- The ions can be distinguished by color.
- Here are some common examples:
- Lead forms $Pb^{4+}$ and $Pb^{2+}$
- Iron forms $Fe^{2+}$ → Colorless
- $Fe^{3+}$→ Brown
S2.1.2 – Ionic Bonds
Ionic Bond:
- Refers to the electrostatic attraction experienced between the electric charges of a cation or anion.
- These ARE POLAR
Ionic Character:
Two ways to predict:
- Position on the Periodic Table
- Electronegativity differences
1. Position on the Periodic Table
- Metals on the left side of the zigzag line tend to lose electrons
- Non-metals on the right side of the zigzag line tend to gain electrons.
- The highest tendency to form ionic compounds will be between elements on the bottom left with elements on the top right.
2. Electronegativity
- 1. Differences greater than 1.8 are ionic.
- 2. Electronegativity is given in the data booklet
Polyatomic Ions:
- Ions that contain more than all atoms
Naming Ionic Compounds:
- The name of the cation is given first and is followed by the anion
- Cations adopt the name of the parent atom and the name remains unchanged
- Monatomic anions adopt the first part of the name of the parent atom, followed by the suffix “-ide”. If the anion is polyatomic its name remains unchanged.
- The name of the compound does not reflect the number of ions in the formula
S2.1.3 – Lattice and Properties of Ionic Compounds
Lattice Structure:
- The ions in ionic compounds surround themselves with ions of the opposite charge.
- Because of this, ionic compounds have three-dimensional crystalline structures known as ionic lattices.
Lattice Enthalpy:
- Energy needed to break lattice bonds
- Smaller the ion → greater charge → higher lattice enthalpy
- For example: NaCl or KCl
- NaCl > KCl because Na has smaller radius
- Higher lattice enthalpy of NaCl
- Smaller ions size → more lattice enthalpy· The formula unit is the smallest particle of an ionic compound.
Physical Properties of Ionic Compounds:
- High melting/boiling points.
- Strong electrostatic attraction between ions.
- Large amount of energy is needed to break the bond.
- Compounds are hard and brittle.
- High charge → smaller ion → greater melting point.
- High lattice enthalpy → High melting/boiling point
- NOT malleable or ductile.
Volatility:
- The tendency of a substance to vaporize.
- Vaporize: the ability for something to be converted into vapor
- Ionic compounds have very low volatility
- Due to strong electrostatic forces of attraction between oppositely charged ions.
Solubility: → → →
- Ability of solid to dissolve in a liquid to become a solution.
- Solubility trends are based on the similarity of the chemical nature of the solute and the solvent.
- Polar compounds dissolve in polar solvents.
- Nonpolar compounds dissolve in nonpolar solvents
Electrical Conductivity:
- Ability to conduct electricity.
- Requires free moving ions
- Molten and dissolved Ionic compounds CAN CONDUCT ELECTRICITY
- Solid ionic compounds do not conduct electricity
- Because the ions are locked into place and are not free to move about.
Brittleness:
- The crystal will shatter when force is applied.
- Ionic compounds tend to be brittle because:
- Ions of like charge can be next to each other in the lattice structure
- The repulsive charges cause the structure to split easily